Evaluation of a new combined SpO2/PtcCO2 sensor in anaesthetized paediatric patients

Background: The recently introduced TOSCA monitor (Linde Medical Sensors AG, Basel, Switzerland) combines pulse oximetry (SpO(2)) and transcutaneous PCO2 (PtcCO(2)) monitoring in a single ear sensor. The aim of the present study was to evaluate accuracy of the TOSCA monitor to estimate SaO(2) and PaCO2 in anaesthetized children. Methods: With approval of the hospital ethical committee and after obtaining informed parental consent, the TOSCA sensor was attached to one ear lobe of anaesthetized children in whom arterial access was established for cardiac catheterization or invasive blood pressure monitoring. SpO(2)(Tosca) and PtcCO(2) as well as SpO(2)(Finger) and PECO2 values from the anaesthesia monitoring (AS5; Datex-Ohmeda, Helsinki, Finland) were compared with SaO(2) and PaCO2 values from arterial blood gas analysis. Corresponding data were compared using Bland Altman bias analysis. Results: A total of 111 blood samples were taken from 60 children (median age: 4.41 years; 0.35-16.13 years). SaO(2) values ranged from 63 to 100% (median: 98.7%), PaCO2 ranged from 3.8 to 7.3 kPa (median: 4.6 kPa). Mean difference (+/-2 SD) between PaCO2 and PtcCO(2) was -0.035 kPa (+/-0.74 kPa), between PaCO2 and PECO2 0.002 kPa (0.73 kPa), respectively (1 kPa = 7.3 mmHg). Bias and precision between SaO(2) and SpO(2)(Tosca) was -0.63% (+/-2.77%) and 0.13% (+/-4.52%) between SaO(2) and SpO(2)(Finger). Conclusions: In anaesthetized children, the TOSCA ear sensor allows estimation of SaO(2) and PaCO2, comparable in accuracy to endtidal capnometry and finger pulse oximetry. This makes the TOSCA monitor a helpful add-on to respiratory monitoring in anaesthetized children, in situations, in which endtidal capnometry is unreliable or difficult to establish.